Snap switch having means for moving a second contact towards a first contact prior to engagement thereof



July 19, 1966 A D. J. ROGERS .7 3,261,935

SNAP SWITCH HAVING MEANS FOR MOVING A SECOND CONTACT TOWARDS A FIRST CONTACT PRIOR TO ENGAGEMENT THEREOF Filed Sept. 25, 1964 f z Sheets-Sheet 1 FIGI 34 INVENTOR DONALD J. ROGERS BY {546% M4 JAM ATTORNEY July 19, 1966 n. J. ROGERS A A A 3,261,935

SNAP SWITCH HAVING MEANS FOR MOVING A SECOND CONTACT TOWARDS A FIRST CONTACT PRIOR TO ENGAGEMENT. THEREOF Filed Sent. 25, 1964 A I 2 Sheets-Sheet 2 92 A l 80 H05 7 INVE NTOR T DONALD J. ROGERS BY %5 ac a! A ATTORNEYJ United States Patent 3,261,935 SNAP SWITCH HAVING MEANS FOR MOVING A SECOND CONTACT TOWARDS A FIRST CON- TACT PRIOR TO ENGAGEMENT THEREOF Donald J. Rogers, Lancaster, Pa., assignor to Hamilton Watch Company, Lancaster, Pa., a corporation of Pennsylvania Filed Sept. 25, 1964, Ser. No. 399,205 13 Claims. (Cl. 200-67) This invention relates to electric arc prevention in electric rewind devices and more particularly to a snap acting switch for minimizing arcing in electrically rewound time totalizing meters.

In assignees co-pending application, Serial No. 228,994, filed October 8, 1962, there is disclosed a snap action switch for use in a miniature time totalizer. Devices of this type are used to monitor the running time of various electrical equipment and take the form of spring driven watch or clock mechanisms which are periodically electrically rewound by the energizing current of the equipment being monitored. For example, in monitoring the running time of a marine engine, the running time meter is conventionally coupled to the engine electrical circuit so that the electrical rewinding impulse comes from the ignition circuit of the motor. The closing of the switch contacts energizes an electromagnet to impart a physical rewind force to a rotor. Rewinding movement of the rotor breaks the electrical contact, opening the circuit and rewinds the main or drive spring of the meter. The main spring then runs down through an escapement mechanism driving the indicator hands of a watch or clock type dial indicator until such time as the switch contacts again close and the entire cycle is repeated. Since the device relies upon the ignition circuit of the motor or other apparatus being monitored it will not run for any appreciable length of time if the motor is not energized. The rundown time of the drive is relatively short, i.e., on the order of several seconds to a few minutes. As a result, the movement of the indicator hands is proportional to the running time of the engine.

The output shaft of the time totalizing meter providing a useful indication is coupled to the rotor through a one- Way clutch such that the output shaft is de-clutched from the rotor during rewind. During the time that the drive springis unwinding the rotor positively drives the output shaft through the one-way clutch and because the load on the rotor is substantial, the rotational movement of the rotor is necessarily slow. The slow movement of the rotor presents serious arcing problems as the contacts near closure which arcing results in pitting of the contacts and excessive wear, thus substantially decreasing the life of the uni..

In the afore-mentioned co-pending application this areing problem is overcome by providing apparatus for declutching the rotor from the output shaft just prior to switch closure. In this way the full force of the drive spring is able to act on the rotor free of the output load and causes the rotor contact to accelerate so as to produce a snap closure of the switch contacts which minimizes arcing. However, the switch closure system of that application requires additional mechanism for unlocking the unidirectional clutch just prior to switch closure and necessitates a certain amount of clutch adjustment to provide for satisfactory operation.

The present invention provides a snap closure switch for running time meters and the like of relatively simplified inexpensive construction which completely eliminates the need for unlocking the unidirectional clutch. The present invention is based upon the provision of one or more permanent magnets which, as the contacts near closure, exert a magnetic force on the rewind armature causing the armature contact to snap toward the rotor contact. In the preferred embodiment of the present invention permanent magnets are provided on both the rotor and the armature such that a torque on the relay armature is developed by a repulsion force between adjacent poles of the magnets. The snap closure is effected through this arrangement by providing the maximum possible magnetic force when the contacts are at their maximum airgap. This force decreases to minimum absolute value when the contacts are closed. Thus, maximum acceleration is obtained when it is most needed but diminishes as the contacts actually meet so as to not only reduce arcing during closure but likewise reduce the effects of contact bounce. The device of the present invention is not only of inexpensive construction, but is highly reliable in operation.

It is therefore one object of the present invention to provide a novel snap closure switch.

Another object of the present invention is to provide a magnetic snap closure switch.

Another object of the present invention is to provide snap closure of switch contacts through the application of magnetic repulsion forces.

Another object of the present invention is to provide a snap closure switch utilizing one or more permanent magnets.

Another object of the present invention is to provide a time totalizing meter incorporating arc prevention switch closure means.

Another object of the present invention is to provide a running time meter of relatively simplified inexpensive construction and more reliable operation.

These and further objects and advantages of the invention will be more apparent upon reference to the following specification, claims, and appended drawings, wherein:

FIGURE 1 is an exploded view of a time totalizing or running time meter constructed in accordance with the present invention;

FIGURE 2 is a plan view of the apparatus of FIG-.

URE 1;

FIGURE 3 is a front elevation of the apparatus of FIGURE 2;

FIGURE 4 is a plan view of a preferred embodiment of the present invention;

FIGURE 5 is a simplified wiring diagram for the meter of the invention; and

FIGURES 6, 7 and 8 illustrate the repulsion forces acting on the contacts juts prior to and at closure in the embodiment of FIGURE 4.

Referring to the drawings, FIGURE 1 is an exploded view of the time totalizing meter of the present invention generally indicated at 10 which is of approximately pocketwatch size construction and incorporates many of the features of a more or less conventional watch. The meter comprises an output or drive shaft 12 coupled through a conventional gear train and escapement mechanism indicated by the block 14 to a pair of watch dial indicator hands 16 and 18. The escapement mechanism 14 includes the conventional balance in the form of a balance wheel and hairspring which controls the unidirectional movement of the output shaft 12.

Shaft 12 includes a reduced diameter portion defining a hub 20 over which passes an aperture 22 formed in an elongated rectangular rotor 24. Rotor 24 is freely received over the hub 20 so that the rotor may rotate with respect to the output shaft 12 about hub 20. Also received over the upper end of the hub 20 is a circular clutch disc 26 which fits on the hub 20 with a press or friction fit so that the clutch disc 26 and output shaft 12 rotate in unison. Clutch disc 26 is received over the hub by means of its central aperture 28.

The outer end of rotor 24 is provided with a pin 30 engaging the end 32 of a helical coiled mainspring 34. The other end 36 of the mainspring .is suitably secured to a stationary portion of the meter support or case (not shown).

Also mounted on rotor 24 are a pair of pivot pins 38 and 40 which rotatably receive clutch pawls 42 and 44. These pawls are provided with suitable apertures 46 and 48 adapted to slide over the pins 38 and 49 so that the pawls are free to pivot about the pins. The pawls themselves carry pins 50 and 52 to which are secured the ends 54 and 56 of a helical clutch tension spring 53.

As best seen in FIGURE 2, the rightmost outer end of the rotor 24 is provided with an L-shaped flange portion 60 carrying a first switch contact 62. This portion of the armature also carries a ferro-magnetic plate 64 adapted to cooperate with a permanent magnet 66 mounted in the end of an armature arm 68. Armature arm 68 includes an upstanding tab 70 in which is received the second switch contact 72.

Armature arm 68 forms the extreme outer end of the armature 74 of a drive motor assembly generally indicated at 76. The motor assembly includes a generally rectangular housing 78 in which is mounted the coil 80 of FIGURE which coil surrounds an iron core 82. Core 82 terminates adjacent the other end 84 of the armature 74 and acts as a stop limiting the clockwise movement of the armature about its pivot 86. The armature is pivoted by means of a pair of lugs 75 and 77 formed integral with it and extending through suitable apertures 87 and 89 in the upper and lower surfaces of the housing 78. The armature is biased to its extreme counterclockwise position by a leaf spring 88 riveted as at 90 or otherwise suitably secured to the enlarged end portion 84 of the armature. The other end of the leaf spring may be suitably secured to the backwall 92 of the housing.

In operation and referring to FIGURE 2, when the mainspring 34 is completely wound, that is stretched to its maximum extent, it acts against the end of the rotor to cause the rotor 24 to rotate in a counterclockwise direction as indicated by the run arrow in FIGURE 2. During this time clutch spring 58 causes the pawls 42 and 44 to bear against and frictionally engage with the edges of the clutch plate 26 so that the clutch plate 26 rotates in the counterclockwise direction along with the rotor 24. Since the clutch plate is frictionally mounted to the output shaft, the output shaft 12 likewise rotates to drive the indicating hands 16 and 18 through the gear train and escapement 14.

As contacts 62 and 72 near each other, permanent magnet 66 exerts a force of attraction upon the ferromagnetic material of plate 64 which action causes the armature end 68 to snap towards the end of the rotor overcoming the biasing force of leaf spring 88. As soon as contacts 62 and 72 close a circuit is completed from the battery 92 in FIGURE 5 through these contacts to the coil 80 which energization polarizes the magnetic core 82 of the coil further drawing the large end 84 of the armature in towards the core. The result is that a clockwise motion is imparted to the armature about pivot 86 and this force is applied through the now joined contacts 62 and 72 to the rotor 24. The rotor is physically pushed or impulsed in a clockwise or wind direction and at this time the contoured surfaces of the pawls 42 and 44 cause them to slip along the edges of the clutch 26 so that the clutch is effectively disengaged, permitting the rotor to rewind in the clockwise direction so as to wind the mainspring 34. The inertial forces of the rotor 24 cause the contacts 62 and 72 to separate thus breaking the circuit to coil 80 and de-magnetizing the electromagnet of the drive assembly. When the rotor reaches its maximum point of rewind, that is once the inertial forces of the rotor are overcome by the rewinding mainspring 34, the rotor stops and commences a second cycle of counterclockwise running. At this time, the pawls [it again frictionally lock to the edges of the clutch disc and the output shaft is driven.

FIGURE 4 shows a modified and preferred embodiment of the present invention with like parts bearing like reference numerals. This embodiment is in all respects similar to the embodiment previously described with the exception that the end 68 of the armature 74 is turned over as at 94 and carries a permanent magnet 96. In addition, the rotor 24 is provided with an additional flange 98 carrying a second permanent magnet 1th). The magnets are positioned such that like poles face each other to provide a force of repulsion between the magnets. For the sake of illustration, FIGURES 6, 7 and 8 show the magnets 96 and 100 with adjacent north poles but it is understood that they both may be reversed so as to have the south pole of each facing the other magnet.

FIGURE 6 illustrates the magnets and contacts near the end of a running cycle when the rotor 24 and permanent magnet 1% along with rotor contact 68 approach armature contact 72. In the position illustrated in FIG- URE 6, very little overlap exists between the adjacent north faces 102 and 164 of the permanent magnets and hence little torque is developed due to any repulsion forces between the magnets.

In FIGURE 7 the magnets and contacts are shown at the position of maximum airgap. This position is empirically determined by the voltages and other parameters of the system and is of such size as to insure that no arcing will occur between contacts 68 and '72. At the position illustrated in FIGURE 7 it is desirable that closure be effected as rapidly as possible to minimize arcing. At this position the contacts are still slightly separated and the adjacent faces 102 and 104 of the magnets completely overlap so that a maximum force of repulsion occurs between the magnets. Since the rotor 24 is still coupled through the one-way clutch including clutch disc 26 to the output shaft 12, the load on this output shaft prevents any substantial acceleration of the rotor contact 68 towards the armature contact 72. However, the converse is not true since the armature 74 is only biased into the rest position by the relatively light leaf spring 88. Thus the armature is free to move against the bias of the leaf spring and when the magnets are in the position illustrated in FIGURE 7 a force of repulsion is developed through magnet 26 on the turned over end 94 of the armature which has a substantial torque component about pivot axis 86. This causes the armature to rapidly rotate about pivot 86 in a clockwise direction so as to rapidly close the contacts, that is bring them to engagement, which position is illustrated in FIGURE 8. This initial movement of the armature is then supplemented upon contact closure by the energization of the coil of the electromagnet which causes the armature to be completely drawn into the core 82 which further rotation of the armature supplies a physical backward push to the rotor initiating the rewind cycle.

It is an important feature of the embodiment of FIG- URE 4 that the maximum force of repulsion occurs just prior to contact closure when maximum acceleration forces are most desired and that this force of repulsion diminishes as the contacts approach the closure position of FIGURE 8. This diminishing in force occurs because the amount of overlap of the like pole faces 102 and 104 of the permanent magnets diminishes as the elements move from the position of FIGURE 7 to that of FIGURE 8. The accompanying decrease in the repulsion force and hence acceleration force applied as a torque to the armature helps to minimize contact bounce and any arcing and wear which may be occasioned by this undesirable aspect of contact closure.

It is apparent from the above that the present invention provides a novel snap closure switch particularly suited for use in spring driven, electrically rewound time totalizing meters and running time meters. However, the snap closure switch of the present invention also finds utility in a wide variety of other switching applications. It provides snap closure of the switches in an electro-mechanical arrangement which substantially reduces cost, complexity, and the assembly time of the unit. The snap closure switch completely eliminates the necessity for de-clutching the one-way clutch just prior to switch closure and makes unnecessary the apparatus for effecting this de-clutching. The arrangement is particularly suited for small timing units of approximately pocketwatch size and in addition to its simplicity is highly reliable in operation.

In the preferred embodiment illustrated in FIGURE 4, both the armature and rotor are provided with permanent magnets having like poles facing to provide a repulsion force between the magnets. In FIGURE 1 the force of attraction between permanent magnet 66 and ferro-magnetic plate 64 is utilized to effect snap closure. It is apparent that in place of the ferro-magnetic plate a second permanent magnet may be utilized in the embodiment of FIGURE 1 and positioned so that unlike poles of the two permanent magnets face each other. However, the embodiment of FIGURE 1 is not as satisfactory as the arrangement of FIGURE 4 since the acceleration forces producing movement of the armature increase as the contacts approach closure tending to increase rather than minimize contact bounce as in the preferred embodiment of FIGURE 4.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A snap closure switch for a unidirectional drive comprising drive means and a driven member, one-way clutch means including a first movable contact coupling said drive means to said driven member, a second contact positioned in the path of movement of said first contact, and means for moving said second contact toward said first contact just prior to engagement of said contacts.

2. A switch according to claim 1 wherein said first contact is mounted on a rotor, said drive means including a spring for driving said rotor.

3. A snap closure switch for a unidirectional drive comprising a driving member and a driven member, said driving member alternately moving in first and second directions, said driving member including a first contact, a second contact positioned in the path of movement of said first contact, one-way clutch means coupling said driving member to said driven member, said driving member when moving in said first direction acting to drive said driven member through said clutch means and to simultaneously move said'first contact toward said second contact, said one-Way clutch means being disengaged when said driving member moves in said second direction, and means for causing said second contact to move toward said first contact just prior to engagement of said contacts.

4. A switch according to claim 3 wherein said second contact is mounted on movable member, and said second contact moving means comprises permanent magnet means acting between said driving member and said movable member.

5. A snap closure switch for a unidirectional drive comprising a rotor, a first contact carried by said rotor,

first means for driving said rotor in a first direction, second means including a second contact for driving said rotor in a second direction, a driven member, one-way clutch means coupling said rotor to said driven member whereby said driven member is driven by said first drive means through said rotor and said clutch, and means for moving said second contact toward said first contact just prior to engagement of said contacts.

6. A snap closure switch for a unidirectional drive com- I prising a rotor, resilient means for driving said rotor, a first contact carried by said rotor, an armature carrying a second contact in the path of movement of said first contact, a driven shaft, one-Way clutch means coupling said rotor to said driven shaft, and permanent magnet means acting between said rotor and armature to cause said second contact to move toward said first contact just prior to engagement of said contacts.

7. A switch according to claim 6 wherein said drive means comprises a spring, and electromagnetic means including said armature for rewinding said spring through said rotor.

8. A switch according to claim 7 wherein said permanent magnet means exerts a force of attraction between said rotor and armature.

9. A switch according to claim 7 wherein said permanent magnet means exerts a force of repulsion between portions of said rotor and armature.

10. A switch according to claim 9 wherein said permanent magnet means comprises a first permanent magnet mounted on said rotor and a second permanent magnet mounted on said armature with the like poles of said magnets facing each other as said contacts near engagement.

11. A snap closure switch for a unidirectional drive comprising a rotor, a spring for driving said rotor in one direction, an electromagnet including a pivoted armature for driving said rotor in the opposite direction to rewind said spring, an output shaft, one-way clutch means operatively coupling said output shaft to said rotor during movement of said rotor in said one direction and dis-connecting said output shaft from said rotor during movement of said rotor in said opposite direction, a first contact carried by said rotor, a second contact carried by said armature in the path of movement of said first contact, and permanent magnet repulsion means for applying a torque to said armature to cause said second contact to move toward said first contact just prior to engagement of said contacts.

12. A switch according to claim 11 including indicating means, and escapement means coupling said output shaft to said indicating means.

13. A switch according to claim 11 wherein said oneway clutch comprises a clutch disc connected to said output shaft, a pair of pawls pivoted to said rotor, and spring means biasing said pawls into contact with the edges of said clutch disc.

References Cited by the Examiner UNITED STATES PATENTS 1,763,003 6/1930 Mead.

2,180,701 11/1939 Wilson.

2,984,722 5/1961 Smith et a1.

ROBERT K. SCHAEFER, Primary Examiner. KATHLEEN H. CLAFFY, Examiner.

D. SMITH, JR., Assistant Examiner. 

1. A SNAP CLOSURE SWITCH FOR A UNIDIRECTIONAL DRIVE COMPRISING DRIVE MEANS AND A DRIVEN MEMBER, ONE-WAY CLUTCH MEANS INCLUDING A FIRST MOVABLE CONTACT COUPLING SAID DRIVE MEANS TO SAID DRIVEN MEMBER, A SECOND CONTACT POSITIONED IN THE PATH OF MOVEMENT OF SAID FIRST CONTACT, AND MEANS FOR MOVING SAID SECOND CONTACT TOWARDS SAID FIRST CONTACT JUST PRIOR TO ENGAGEMENT OF SAID CONTACTS. 